Process for the treatment of an aqueous solution containing various metal sulphate salts for the recovery of metal values, particularly of cobalt, therefrom



Feb. 2, 1965 C. M. BARUT ETAL PROCESS FOR THE TREATMENT OF AN AQUEOUSSOLUTION CONTAINING VARIOUS METAL SULPHATE SALTS FOR THE RECOVERY OFMETAL VALUES, PARTICULARLY OF COBALT, THEREFROM Filed Aug. 28, 1962AUTOCLAVE Preuure=26 Pslg Llquor Temperature Ambient 4 PH 0.9- L: 2vCu$0 ZIISO4 Wash Water 8 IB- I FILTER (mom Oak. Gypuum 9 NEUTRALIZATION"2 4 PH -e.s P-|2 DlSSOLVER 4 H80 FILTER 4 Gyp'um Fllirate To 605 Cakewaste 6 psurn Film". T0 line y Rccovory RNYC" To 99" To Cobalt RccovaryINVENTORS Cihaf M. Baruf Raymond O. Lehr United States Patent 3,168,375PROCESS'FOR THE TREATMENT OF AN AQUEOUS SOLUTION CONTAINKNG VARIOUSMETAL SUL- PHATE SALTS FOR THE RECOVERY OF METAL VALUES, PARTICULARLY 0FCOBALT, THERE- FROM I Cihat M. Barut, New York, N.Y., and Raymond O.Lehr, Westport, Coma, assignors to Dorr-Oliver Incorporated, Stamford,Conn, a corporation of Delaware Filed Aug. 28, 1962, Ser. No. 219,964 11Claims. (Cl. 23-435) This invention relates to improved process forrecovering metal values from ores or analagous materials and moreparticularly to a process for the selective recovery of cobalt valuesfrom an aqueous solution thereof.

Cobalt is a very important and critical chemical material. The amountsof this metal which occur in nature are relatively small, therefore,whenever this metal occurs in an orc, industrial by-products, orchemical and metallurgical process liquors attempts are made to recoverthis essential element.

The methods which have heretofore been proposed for recovering thismetal vary, in general, with the nature of the starting material.However, in general, these processes leave much to be desired from thecommercial point of view, especially as to the recovery of this metalfree from impurities. The art is, therefore, confronted with the problemof recovering cobalt values from these materials in an economical andcommercially acceptable manner.

It is, therefore, an object of this invention to provide a process forthe recovery of cobalt values contained in an aqueous solution in anetficient and economical manner.

It is another object of this invention to provide a process forrecovering cobalt values from an aqueous solution substantially freefrom other metals.

The separation and recovery of cobalt values from aqueous solutions isfurther complicated when said solution contains excess amounts of zinc.The prior art methods of separating zinc from the aqueous solutioninvolve complex reactions which generally yield incomplete separation ofions.

It is, therefore, another object of the present invention to recovercobalt from a solution high in zinc values.

It is a further object of this invention to provide a process forrecovering metal constituents from aqueous solutions which will lendthemselves to further processing to obtain the free metals.

It has been found, in accordance with the present invention, that cobaltcan be recovered in a highly efficient and economical manner from anaqueous cobalt solution containing zinc and other metal constituents byreacting said solution with hydrogen sulphide gas at a pressure withinthe range of 20-30 pounds per square inch gauge and at a pH maintainedwithin the narrow range of 0.9 to 1.2. The liquors resulting from thisreaction are amenable to the extraction of cobalt either in the form ofpure metal or pure cobalt compounds.

In order that this invention may be readily carried into effect thisinvention will now be described with reference to the accompanyingdiagrammatic drawing which illus trates the preferred embodiment of thisinvention.

Referring to the drawing, an aqueous solution, such as copper tankhouseprocess liquors containing essentially cobalt sulphate, copper sulphateand zinc sulphate, is introduced into an autoclave 2 via line 3 andadjusted to a pH in the range of 0.9 to 1.2, preferably, by addingpreviously precipitated cobaltous hydroxide via line 4. The resultingmixture is then reacted with hydrogen sulphide gas introduced via line 5under a pressure of about 20 to 30 pounds per square inch gauge,preferably r 3,168,375 Patented Feb. 2, 1965 at 25 p.s.i.g., at roomtemperature. This pressure is maintained until the reaction reachesequilibrium. Under the aforesaid conditions, copper and zinc sulphateprecipitates as thesulphides but cobalt remains in solution as cobaltsulphate.

Since the conversion of copper and zinc-sulphate to the sulphides isaccompanied by the formation of sulphuric acid, it is essential that thereaction mixture be constantly checked to maintain the pH within theaforesaid range. Any of the conventional methods of determining andcontrolling pH may be employed. These methods may be either automatic ormanual.

The contents of the autoclave are conducted via line 6 to a filter 7,preferably a pressure filter, wherein the cobalt sulphate solution isseparated from the precipitated copper and zinc sulphide. The filtercake, prior to removal from the filter, is washed, with .wash waterintroduced via line 8 to remove residual aqueous cobalt solutionremaining in the cake and then conducted via line 9 to dissolvingstation 10 for further treatment.

The filtrate, comprising aqueous cobalt sulphate in reaction liquors, isconducted via line 11 to a neutralization station 12 where the pH of theliquor is raised to about 8.3 by adding an alkali, preferably calciumhydroxide, via line 13 to precipitate cobaltous hydroxide and gypsum.This mixture is conducted to a filter 15 via line 14, such as a rotarydrum filter, wherein a filter cake comprising cobaltous hydroxide andgypsum is formed.

The filtrate from this filtering operation is discarded to waste vialine 16. The filter cake is removed and conducted to a cobalt recoverycircuit via line 17.

A portion of the freshly precipitated cobaltous hydroxide and gypsum ispreferably removed via line 18 and recycled to the autoclave 2 via line4 to act as a pH control. The gypsum which is recycled acts as a filteraid in filtration station 7.

Reverting to the dissolving station 10, the filter cake, formed onfilter 7 and conducted to the dissolving station 10 via line 9,comprises precipitated zinc sulphide and copper sulphide and gypsum,which was recycled to the autoclave 2 with the cobaltous hydroxide asheretofore described.

The filter cake in dissolving station 10 is reacted with sulphuric acidvia line 19 whereby the zinc sulphide is converted to zinc sulphate withthe generation of hydrogen sulphide gas. The regenerated hydrogensulphide may be removed via line 20 and reused in the autoclave 2 vialine 5 as heretofore described.

Thereaction mixture is conducted via line 21 to a filter 22 such as arotary drum filter, wherein the aqueous zinc sulphate is separated fromthe remaining copper sulphide and gypsum. The filtrate comprising zincsulphate is removed via line 23 and conducted to a zinc recoverystation, the filter cake, comprising copper sulphide and gypsum, isremoved from the filter drum and conducted via line 24 to a copperrecovery station.

In the method of the present invention it was found that improvedfiltration of the zinc and copper sulphide was obtained if a residualamount of the reaction mixture of the preceding reaction was retained inthe autoclave during the subsequent reaction. It is believed that theprecipitated zinc and copper sulphide crystals act as nuclei during thesubsequent precipitation thereby forming large crystals which filterrapidly.

One of the features of the present invention is that, preferably, thealkali added to the neutralization station 12 forms a precipitate whichmay act as a filter aid in the filtration station 7.

This invention will be better understood from a conis not limitedthereto:

7 Example I consumptionof hydrogen sulphide in the process. Thecobaltous'hydroxide required for the pH: control inthe autoclave can beobtained by recycling part ofthe previously precipitated cobalt.

A Solution Was P p to cottespond a yp 5 A still further advantage 'isthat thejcalcium hydroxide copper tahkhouse d h lhp hslhg Sulphate hadded to the aqueouscobalt sulphate solution, after sep- Of Cobalt, oppmg Zlhc- Upohahalysls, the Solutloh aration of copper and zinc sulphide,formsa gypsum Was found Q V precipitate which upon recycling to .theautoclave acts l "Grams E liter. 7 as a filter aid in the subsequentfiltration operation. Cobalt 510 It is to be understood that suitablemodifications to COPP the teaching of this invention may be made withoutde- Ziflc Z- parting from the spirit thereof. For instance, calcium Toone liter of the above liquor, 2.90 grams of cobalt, oxide, calciumcarbonate and magnesium hydroxide may as freshly precipitated cobaltoushydroxide wasadded", he d .cohtrolhhg the P 0f the Process hquors 111 ina stainless steel container and thoroughly mixed. the ahtohlave- I V Thecontainerwas placed'in an autoclave and hydrot any alkah cansubstlttlted f9r ca1Cmm gen sulphide was ap a pressure f 25 rpr'sigydroxlde. Examples are calcium oxide, calc um carbonfor a period of twoand a half hours withconstant agitae ate h hanum hydtoxlde- I tion. Theautoclave was maintained" at room temperature. It 'also'to understoodthat 111 the p t'p The pH at the completion of the reaction was recordedthe material' y he p m continuously in as 1.00. Theproduct of thereaction was filtered and batches, of p 0f the fiOWSheet y be continuousand washed. The results are. reported as follows: 7 part of it inbatches. For instance, the autoclave op- Ccs. or Go, g .p.l. or C0,Ou,g.p.l. Cu, Zn,g.p.l. Zn, Zn:( l0 grs. percent grs. .or percent grs.or percent grs. Ratio Feed solution to autoclave 1,000 cc.-- 4.7 g.p.l.-4.70 0.24 g.p.l 0.24 12.9 g. 1.... 12.9 2.74:1 Filtrateiromreaetion withwashings. 1,405 cc- 5.4 g.p.l 7.60 none 0.018'gpl 0.025 0.0033:1 Filtercake from reactlon nu. 24.1 gr- 0.39% 0.094 0.35% 0.085 51.9% .50 133:1

Example II a eration may be a batch-type operation. However, in theAnother solution substantially identical to the solution Subsequent hfilter. may be so slzed a a so that the filtration operatlon 1Scontinuous. prepared rnExample I was prepared and reacted under F {ha fn d f th i0 mbodi the conditions set out above except that the reactionwas 3 i i 0 e us f stopped afterone and 'a half hours. Theresults were iof i mvamlon t Is cvldent t t 6 objects found to be Substantially thg sthls invention, togetherwith many practical advantages,

. I v are successfully achieved. While the preferred embodi- E l 111mentsot'our' invention have been described, numerous furthermodifications may be made without departing A Solutlon was P to ftypical 4.0 from the scope of the invention as defined by the apcoppertankhouse d scard liquor using the sulphate salts pended claims I ofcobalt, copper and zinc. Upon analysis the solution was found to containa p Therefore, it is to be understood that all matters here- Grams perliter in set torth as shown in the accompanymgdraw ng are Cobalt 7 3.9to be interpreted in an illustrative and not in a limiting Copper -J.0.40 3;? Zinc 12.1 I clalm- 1. A process for treating an aqueoussolutlon contain- TO one liter of the above solution grams of P ing thesulphate salts of zinc and cobalt comprising the dered magnesium oxidewas added in a stainless steel cont p f, dj ti g th H lu of h l i toWithin 'tainer. and thoroughly mixed. The container was-placed the rangeof 0.9 to 1.2 reacting said solution with hydroin an autoclave andhydrogen sulphide was applied under gen sulphide at a pressure withinthe range of 20 to 30 a pressure of 26 p.s.i.g. for a period of 2.5hours with conp.s.i.g., maintaining said solution within the aforesaidpH stant agitation. The pH at completion of the reaction was rangeduring said reaction to precipitate zinc sulphide, recorded as 0.9. Theproducts of the reaction were filand separating the thus precipitatedzinc sulphide from tered and Washed, the results. are reported; asfollows: '55. the aqueous cobalt solution.

grs. I percent grs.- 7 or percent grs. 01' percent grs. Ratio Feedsolution to autoclave 995 cc"... 3. 88 12.1 g.p.l. 12. 1 3. 08:1Filtratefromreactionwith was gs. 1,250 cc- 3.70 0.06 g.p.l 0.07v 0.0l9z1Filter cake from reaction 1,840 gr5 0.08 61.0% 11.20 140:1

From the above examples applicants haveshown a method of recoveringcobalt substantially'free of zinc impurities. I V 1 The method 'of thepresent invention possesses a number of important advantages inextracting metal values,

particularly cobalt, from starting materials containing suchvaluesespecially when substantially complete. separa tion of thesevalues from undesirable elements is desired.

The hydrogen sulphide. used can be produced at reasonably low cost fromsulphur and liquid petroleum gas. 7

The hydrogen sulphide consumed by the zinc metal can be regenerated withdilute sulphuric acid and reused in the system, thereby reducing to aminimum the overall 2. A process according to claim l'wherein saidreaction is carried'out' in the presence of previously precipitated zincsulphide.

3. A- process for treating an aqueous solution containingthe sulphatesalts of copper, zinc and cobalt comprising the steps of, adjusting thepH value of the solution to withinl the range of 0.9 to 1.2, reactingsaid solution with hydrogen sulphide at a pressure within the range of20 to 30 p.s.i.g., maintaining said solution with- In the aforesaid pHrange during said reaction to precipitatecopper and zinc as sulphides,and separating the thus precipitated metal sulphides from the aqueous cobalt. solution.

4. A process according to claim 3 wherein said reaction is carried outin the presence of previously precipitatedzinc and copper sulphide.

5. A process for separately recovering metal values from an aqueous feedsolution containing the sulphate salts of copper, Zinc and cobalt whichcomprises the steps of, adjusting the ph value of the solution to withinthe range of 0.9 to 1.2, initially reacting said solution with hydrogensulphide under a pressure of 20' to 30 p.s.i.g., maintaining saidsolution within the aforesaid pH range during said reaction toprecipitate copper and zinc as sulphides, separating the thusprecipitated metal sulphides from the remaining aqueous cobalt solution,subjecting the thus separated metal sulphide precipitate to treatmentwith sulphuric acid to convert zinc sulphide to zinc sulphate,separately recovering the thus formed zinc sulphate from the remainingprecipitate, subjecting the previously separated aqueous cobalt solutionto neutralization treatment to precipitate cobaltous hydroxide, andrecovering the precipitated cobaltous hydroxide substantially free fromimpurities.

6. Process according to claim 5 wherein the hydrogen sulphide generatedduring the conversion of zinc sulphide to zinc sulphate is recycled intothe process for further use.

7. Process according to claim 5 wherein the pH of said feed solution iscontrolled by recycling previously precipitated cobaltous hydroxide.

8. Process according to claim 5 wherein said initial reaction is carriedout in the presence of previously precipitated copper and zinc sulphide.

9. Process according to claim 1 wherein the separated aqueous cobaltsolution is subjected to neutralization treatment to precipitatecobaltous hydroxide, and separating the thus precipitated cobaltoushydroxide from the resulting aqueous solution.

10. A process for recovering cobalt from an aqueous feed solutioncontaining the sulphate salts of zinc and cobalt which comprises thesteps of, adjusting the pH value of the solution towithin the range of0.9 to 1.2, reacting said solution with hydrogen sulphide at a pressurewithin the range of 20 to p.s.i.g., maintaining said solution within theaforesaid pH range during said reaction to precipitate zinc sulphide,filtering the precipitated zinc sulphide from the aqueous cobaltsolution, subjecting said aqueous cobalt solution to neutralizationtreatment with calcium hydroxide to precipitate cobaltous hydroxide andgypsum, and recovering the thus precipitated cobaltous hydroxide andgypsum from the re sulting aqueous solution.

11. Process according to claim 10 wherein previously precipitated gypsumacts as a filter aid during said filtering operation.

Handbook of Chemistry, by N. A. Lange, 10th Edition, 1961, pages 961-963inclusive. McGraw-Hill Book Co., Inc., NY.

3. A PROCESS FOR TREATING AN AQUEOUS SOLUTION CONTAINING THE SULPHATESALTS OF COPPER, ZINC AND COBALT COMPRISING THE STEPS OF, ADJUSTING THEPH VALUE OF THE SOLUTION TO WITHIN THE RANGE OF 0.9 TO 1.2, REACTINGSAID SOLUTION WITH HYDROGEN SULPHIDE AT A PRESSURE WITHIN THE RANGE OF20 TO 30 P.S.I.G., MAINTAINING SAID SOLUTION WITHIN THE AFORESAID PHRANGE DURING SAID REACTION TO PRECIPITATE COPPER AND ZINC AS SULPHIDES,AND SEPARATING THE THUS PRECIPITATED METAL SULPHIDES FROM THE AQUEOUSCOBALT SOLUTION.